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The possible role of group specific component (Gc) (vitamin D-binding protein) in the clearance of cellular actin entering the circulation was examined with 125I-labeled Gc and actin injected into a rabbit model. Although filamentous F-actin is depolymerized primarily by plasma gelsolin, 2 90%

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T-Strains have several characteristics in common with the genus Mycoplasma. Whether or not they are, in fact, mycoplasma has, on occasion, been questioned. One of the main criticisms has been the lack of electron-micrographs showing the morphology of these organisms.Two T-strains from the human genital tract, one from the bovine genital tract and one from the human oropharynx were examined by electron-microscopy. For this purpose, the strains were grown in medium without serum. It was not possible, however, to subculture these organisms in serum-free medium.Cultures of the organisms were incubated for 36 hours at 37°C. Cells were deposited by centrifuging 80 mls of each culture at 60,000 g and then resuspended in 2.0 mls of the supernatent. Fixing the cells with 4.0% glutaraldehyde while still in suspension was found to produce clumps which could not be easily dispersed. Furthermore, addition of 2% phosphotungstic acid to a cell suspension so fixed produced a precipitate which obscured the cells. Uninoculated medium treated in exactly the same way did not exhibit this phenomenon.Specimens were therefore prepared by placing one drop of the cell suspension on carbon-coated grids and fixing in formalin vapour for 30 seconds before staining with phosphotungstic acid. Prepared in this way, cultures were found to contain cells ranging from 800 rnp down to 150 to 160 m p ( FIGURES 1 a and 2). These cells appear to have an asymetric membrane with the outer component being more electron dense than the inner one. Lying outside the limiting membrane is frequently found an envelope of material which is thought to be lipid in nature. Within this envelope there can be seen, on occasion, structures resembling spikes (FIGURE 1 b). Spherical cytoplasmic condensations about 40 to 50 my. in diameter can be seen in most of these cells (FIGURE 2). A further feature is shown in FIGURE 3a, where the cytoplasmic condensations have been liberated from a ruptured cell. It is possible that these represent minimal reproductive units and are shown at a higher magnification in the following FIGURE 3b, where their size is about 65-70 mp.Further studies of behavior in density gradients, examination of ultra-thin sections and an investigation of the relationship of cell size to viability are in progress. The aim of this brief communication has been to suggest that T-strain organisms do not differ fundamentally from other mycopalsma. 391

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